1. Field of the Invention.
This invention pertains to measuring devices, and more particularly to apparatus for determining the quantity of fluid in a reservoir.
2. Description of the Prior Art.
Various products have been developed to indicate the level of fluid within a closed container. For example, sight glasses and float operated needles in combination with calibrated dials are in widespread use. Light beams in conjunction with light sensors are known, such as are illustrated in U.S. Pat. Nos. 3,548,657 and 4,193,004. U.S. Pat. Nos. 3,272,174; 3,713,338; 4,038,650; and 4,069,838 4,287,427; describe different level sensors that employ fiber optics. The aforementioned devices are not generally suitable for measuring the quantity of lubricating oil in internal combustion engines.
U.S Pat. No. 4,322,713 discloses an electronic dip stick that senses a predetermined low fluid level in automotive engines. However, the electronic dip stick of the 4,322,713 patent does not indicate low oil levels approaching the minimum level, and consequently it does not alert a user that the undesirable low level condition is being approached. Renault has introduced an oil level sensor in some of its engines and uses a chip LM1042 specifically designed for this sensor. The Renault Part Number is 327-041-01. This sensor does not employ the dip stick tube for access to the engine. It is threadably and permanently mounted in the engine block.
A need exists for instrumentation which can be used in a wide variety of engines and fluid sensing environments.